I've used the scarves filled with water absorbing crystals, and they work well.
My daughter was using a cooling scarf on a tour in 95+ F, and relatively high humidity. They do help, and stay moist for quite a while.
You might try MEC. You can also find them on Amazon.
Amazon.ca
In the U.S. available at REI:
REI
My wife had a scarf, but also used this method for a little more evaporation.
